Durham, N.C. — The grandfather of a 4-year-old Durham County boy desperately sought help from paramedics and police as his daughter tried to revive the boy at their home four years ago, according to a 911 call played Wednesday during the murder trial of the boy's father.

Joseph Anthony Mitchell, 50, is charged with first-degree murder and two counts of attempted first-degree murder in the Sept. 22, 2010, death of his son Blake and attacks on his older children, Alexis, who was 13 at the time, and Devon, who was 10.

Pete Perolini, the children's maternal grandfather, lived in an apartment built off the garage of the home and said he arrived home about midnight that night and heard a commotion in the house as he was getting ready for bed.

"The ruckus started upstairs, which I had never heard before," Perolini testified. "I heard running going back and forth. It sounded like something was wrong."

He said he went into the house and heard his daughter, Christine, yell at Mitchell, "This is not the time to do anything like this." Then he saw Alexis carrying a limp Blake – "He was like a doll," Perolini recalled – and decided to call police and run to a neighbor's house to summon a nurse.

As prosecutors played a recording of Perolini's 911 call for the jury, he sat at the witness stand and sobbed.

"My grandson, he's 4 years old, we can't wake him up. My son-in-law is locked in a room," Perolini told a 911 dispatcher. "My daughter is up there screaming. Her husband won't come out. I don't know what's going on."

His pleas for help became more desperate as dispatchers in Durham and Orange counties tried to sort out who should respond. The Mitchell house was in Durham County but had a Hillsborough address.

"We need a hell of a lot of help here," Perolini told the dispatcher. "We think the boy is dead. We don't know why. My son-in-law, we don't know where he is. We think he's in a room upstairs."

He described Joseph Mitchell as "a calm, easygoing guy" but noted he had been out of work for a year.

Christine Mitchell could be heard screaming hysterically early on during the call, but when Perolini handed the phone over to her, she became calm and focused as the dispatcher talked her through performing CPR on Blake.

Once first responders arrived at the house, the call became somewhat garbled, but Alexis and Devon could be heard crying in the background, and Christine Mitchell told her father, "I need you Daddy."

Earlier Wednesday, Dr. Deborah Radisch, the state medical examiner who performed the autopsy on Blake, testified that he died of asphyxia and that a "pattern injury" on his neck suggested that his airway was choked off. It would have taken several minutes for the boy to die under those circumstances, she said.

A Durham County Sheriff's Office investigator testified Monday that the injury to Blake's neck matched a bracelet his father wore.

Radisch said under cross-examination that Blake showed no signs of previous abuse.

The defense contends that Joseph Mitchell was a decent father who had a "parasomnia event" because he was under extreme stress and hadn't slept well in months. They said he wasn't aware of his actions that night and shouldn't be held responsible for them.

Prosecutors dispute the so-called "sleepwalking defense," saying Mitchell was completely aware of his actions that night.

After attacking the children, he went into a home office and stabbed himself three times in the chest and slit his throat, and deputies had to break through the door to get to him, according to testimony.